It is known in the relevant art to analyze body fluid samples such as, for example, blood, plasma, urine, and interstitial fluid, may be analyzed for various components or properties. Such components or properties may include, for example, glucose, cholesterol, pathogens, drugs of abuse, coagulation, and haematocrit. In a typical test procedure, the body fluid sample is applied to a test zone containing one or more reactive ingredients. A reaction occurs in the test zone, and an analysis result is produced. An instrument may be used to read the analysis result, or the analysis result can be interpreted by eye using, for example, colour matching or symbols such as bars and/or dots.
A plurality of test zones may be supplied as a linear array of individual test zones along a carrier tape. The carrier tape may be disposed in a housing to form a unit known as a “test cassette.” In a typical configuration, the test cassette may comprise two chambers, one chamber containing unused test material and the other chamber containing used test material. Test cassettes are known for use in laboratory analysers, as well as in portable analysers.
U.S. Pat. No. 4,218,421 issued to Mack et al., discloses a carrier tape with spacings between test zones, the carrier tape housed in a test cassette that has a storage chamber for unused test zones and a storage chamber for used test zones. A barrier means isolates the two storage chambers. U.S. Pat. No. 5,077,010 issued to Ishizaka et al. discloses a cassette housing transparent carrier tape with information fields and test fields. Test fields are read optically from the underside of the tape. Ishizaka '010 also teaches that the motor used to advance the tape, sufficient for a single test, can be guided by marks made along the tape at intervals. These marks can be read by a photoelectric switch. One or more flexible gaskets may be used to keep humidity out of the unused test zone chamber. However, the flexible gasket seal is able to preserve the unused tests for only a few days.
U.S. Pat. No. 7,582,258B2 issued to Ruhl et al. describes a test cassette with separate test zone chambers for the unused carrier tape and the used carrier tape, with a hydraulic sealing means used to prevent moisture entering the unused carrier tape chamber. The sealing means is pressurized by downward pressure applied by a stamp, causing the sealing means to press directly onto the carrier tape and to thus seal the carrier tape against the test cassette. Ruhl '258 also describes a gasket similar to that taught by Ishizaka '010, but utilizes two gaskets inclined in opposite directions to one another. In all embodiments, a deformable gasket is pressed directly onto the carrier tape.
In the above examples of the prior art, a sealing means employed presses a flexible gasket directly onto a carrier tape and creates a drag on the carrier tape as the carrier tape moves through the flexible gasket. Alternatively, the gasket seal may be broken by opening the gasket seal as the carrier tape is advanced, but in so doing the unused test material may be exposed to humidity.